I just stumbled on this place, and as soon as I saw a spaceship model, I suddenly knew I had to start learning how to make some 3D models. I'm owner of SSDC, Inc., an old fashioned RPG company, and one look at the site left me with dancing visions of space ship and robot minis in my head. I'm going to poke around and see what 3D software people recommend. This looks fun!

Cool! I need to experiment a bit with this stuff first. I think I'm going to try something simple first like a Thomas Train/Brio compatible track segment for my sons set, but then maybe a spaceship or two. We have loads of things we could make, like vehicles; who knows where to start. I can always send you a drawing of some a vehicle if you want to take a stab at something.

If you're just learning, Sketchup is super easy and (best of all) free. You can download it here. While Sketchup is great for hard surface models (tanks, planes, buildings, etc) it's not very good for organic or models with a lot of round surfaces. A very easy program for this (also free) is Sculptris. You can get it here.

For more professional tools, you can try Blender, though it's much harder to use and contains a lot of tools that aren't relevant to 3d printing, such as rendering, lighting, animation etc. You can get Blender here.

If you do use Sculptris or Blender (or even if you are using Sketchup) it's a good idea to download netfabb basic to check for errors and resize your model. It can be found here.

You can, of course, use Maya, Max, zBrush, or Autocad. However, if you aren't familiar with these, I would recommend starting with something free until you're comfortable making the purchase (as you're talking $500 - $1000 for a license).

Of the big 4, I would recommend zBrush. It's super easy to make organic and hard surface models (though hard surface takes a bit of technique), uses components similar to sketchup, has customizable brushes, and has a special 3d printing plugin to help with the workflow.

Finally, you can check out my blog for some tricks and tips that I learn, or watch my livestream recordings.